British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Changes in haemodynamic variables during transurethral resection of the prostate: comparison of general and spinal anaesthesia.
We have compared changes in haemodynamic variables before and during transurethral resection of the prostate in 22 patients under general or spinal anaesthesia. In the general anaesthetic group there was a significant decrease in cardiac output (mean 32% (SEM 5%)) and mean arterial pressure (14% (3%)) after induction of anaesthesia and a significant decrease (27% (3%)) in heart rate before the start of resection. ⋯ We conclude that with both these anaesthetic techniques the greatest changes in haemodynamic variables occurred shortly after induction, and that these changes were greater during general than spinal anaesthesia. The resection period was not associated with significant haemodynamic changes.
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Randomized Controlled Trial Comparative Study Clinical Trial
Effects of isoflurane-nitrous oxide and halothane-nitrous oxide anaesthesia on myocardial contractility assessed by transoesophageal echocardiography.
In order to evaluate the direct effect of isoflurane-nitrous oxide and halothane-nitrous oxide anaesthesia on cardiac contractility in 20 adults, we have used a method based on left ventricular end-systolic wall stress (LVESWS) vs velocity of circumferential fibre shortening with corrected heart rate (Vcfc), obtained by transoesophageal echocardiography. We found that LVESWS (index of afterload) decreased significantly with isoflurane-nitrous oxide (n = 10) in concentrations of 1.5-1.95 MAC, but there were no significant changes in LVESWS with halothane-nitrous oxide (n = 10). ⋯ In the analysis of the LVESWS-Vcfc relationship, myocardial contractility associated with isoflurane-nitrous oxide anaesthesia did not differ significantly from that associated with halothane-nitrous oxide anaesthesia at equiMAC concentrations. The results suggest that halothane-nitrous oxide anaesthesia, at 1.5-1.95 MAC, maintained myocardial contractility in similar anaesthetic concentrations to isoflurane-nitrous oxide.
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We have tested a published algorithm for pharmacokinetic model controlled infusion of propofol to supplement 67% nitrous oxide for general anaesthesia in Chinese children aged 4-10 yr. Initially we studied 10 children undergoing minor procedures with spontaneous ventilation; mean duration of surgery was 38 min and mean propofol infusion rate 497 micrograms kg-1 min-1. The precision of the model was 24.8% and bias -18.5%. ⋯ The mean blood concentration required for satisfactory anaesthesia was 6.6 micrograms ml-1 (range 3-11 micrograms ml-1) and the mean blood concentration at the time of waking, which occurred 40 min after switching off the infusion, 0.86 microgram ml-1 (range 0.40-1.45 micrograms ml-1). Our patient population required different pharmacokinetic variables from those in the previous study. Recovery was slow because of the high infusion rates required to maintain satisfactory anaesthesia and large difference between the blood concentration required for anaesthesia and that at which waking occurred.